The present invention relates to a recording apparatus such as a magnetic disk apparatus or the like, in which a rotary disk-shaped recording medium is used, and more particularly, to a recording apparatus having a structure for reducing vibration of the recording medium caused by rotation.
A conventional recording apparatus, for example, a magnetic disk apparatus is generally constructed of a rotary disk-shaped recording medium, an arm provided with a head to read/write from/to this recording medium placed at the end, an actuator to move the head to a predetermined position, a housing to house these components, a control apparatus and an input/output system. It is known of a magnetic disk apparatus that an air flow is created inside the casing by a rotating disk and vibration of the disk called “flutter” occurs due to disturbance of the air flow. When the disk vibrates, the relative positions of the disk and head change, resulting in a problem that the accuracy of reading/writing of information on the disk deteriorates.
One of methods to address this problem is a method of forming in the housing a shroud surrounding and concentric with a disk as described in IEEE TRANSACTION ON MAGNETS, VOL. 35 NO. 5, (1999) PAGE 2301-2303. According to this method, it is possible to suppress input/output of air on the upper side and under side of the disk by providing a shroud and reducing the size of the gap between the shroud and disk and thereby reduce generation of a cyclic secondary flow on the circumferential area of the disk surface and reduce flutter vibration.
Secondly, as described in JP-A-2000-331460 specification, there is another method of placing and fixing a squeeze air bearing plate having a partially ring-shaped smooth surface spreading in the circumferential direction and in the direction of the radius on one side of the disk facing the disk surface with a gap of 0.3 mm or less in between. This method causes a squeeze attenuating force of an air film to act on the disk surface by sufficiently reducing the distance between the disk surface and squeeze air bearing plate to forcibly reduce flutter vibration.
Thirdly, as described in JP-A-2001-167554 specification, there is a method of adopting a two-stage structure of projections and depressions of a cover of a magnetic disk apparatus and narrowing the gap between the cover and disk in the section outside the area in which the arm on the magnetic disk surface traverses compared to the section corresponding to the area in which the arm on the magnetic disk surface traverses. This method suppresses an air flow generated in the gap and reduces fluttering of the magnetic disk.